#include <iostream>
#include <string>
using namespace std;
int main(){
    string s1 ;
    s1 = "1234567890";
    for(int i=0, len=s1.length(); i<len; i++)
        cout<<s1[i]<<" ";
    cout<<endl;
    s1[5] = '5';
    cout<<s1<<endl;
    return 0;
}

#include <iostream>
#include <string>
using namespace std;
int main(){
    string s1, s2, s3;
    s1 = "first";
    s2 = "second";
    s3 = s1 + s2;
    cout<< s3 <<endl;
    s2 += s1;
    cout<< s2 <<endl;
    s1 += "third";
    cout<< s1 <<endl;
    s1 += 'a';
    cout<< s1 <<endl;
    return 0;
}